A small bar magnet is placed with its north pole facing the magnetic north pole. The neutral points are located at a distance r from its centre. If the magnet is rotated by 180^o, the neutral point shall be obtained at a distance of:
1. \(2r\)
2. \(\sqrt{2}r\)
3. \(2^{\frac{1}{3}}r\)
4. \(\frac{r}{2\sqrt{2}}\)

At a place, the angle of dip is 30$°$. If the horizontal component of the earth's magnetic field is B, the total intensity is:

1. $\frac{\sqrt{3}B}{2}$

2. $\frac{2B}{\sqrt{3}}$

3. 2B

4. B$\sqrt{3}$

The earth's magnetic field at a certain place has a horizontal component 0.3 Gauss and the total strength 0.5 Gauss. The angle of dip is:

1. ${\tan }^{-1}\left(\frac{3}{4}\right)$                     

2. ${\sin }^{-1}\left(\frac{3}{4}\right)$

3. ${\tan }^{-1}\left(\frac{4}{3}\right)$                     

4. ${\sin }^{-1}\left(\frac{3}{5}\right)$

Magnetic meridian is :

1.  a point

2.  a line along north-south

3.  a horizontal plane

4.  a vertical plane

The vertical component of the earth's magnetic field is zero at:

1. The magnetic poles.

2. The magnetic equator.

3. The geographic poles.

4. The geographic equator.

A compass needle which is allowed to move in a horizontal plane is taken to a geomagnetic pole. It:

1. will become rigid showing no movement

2. will stay in any position

3. will stay in north-south direction only

4. will stay in east-west direction only

The relative permeability $\left({\mu }_r\right)$ of a ferromagnetic substance varies with temperature (T) according to the curve:

1. A                              

2. B

3. C                              

4. D

A compass needle free to turn in a horizontal plane is placed at the centre of a circular coil of 30 turns and a radius of 12 cm. The coil is in a vertical plane making an angle of 45° with the magnetic meridian. When the current in the coil is 0.35 A, the needle points west to east. The horizontal component of the earth’s magnetic field at the location is:
1. 0.299 G
2. 0.497 G
3. 0.388 G
4. 0.535 G

The material suitable for making electromagnets should have:

1. High retentivity and high coercivity

2. High retentivity and low coercivity

3. Low retentivity and high coercivity

4. Low retentivity and low coercivity

Above Curie temperature:

1. a ferromagnetic substance becomes paramagnetic.

2. a paramagnetic substance becomes diamagnetic.

3. a diamagnetic substance becomes paramagnetic.

4. a paramagnetic substance becomes ferromagnetic.